膨润土对重金属离子的竞争性吸附研究

Effect of Bentonite on Competitive Adsorption of Heavy Metals Ions

通过间歇震荡平衡法研究了膨润土对4种重金属离子Cd2＋、Zn2＋、Cu2＋、Pb2＋的竞争性吸附特性及其机制。研究结果表明：与单一离子体系比较,膨润土在竞争体系中对Cd2＋、Zn2＋、Cu2＋、Pb2＋4种重金属离子的吸附量均呈下降趋势。竞争体系下,其它重金属离子的存在显著抑制了膨润土对Cd2＋的吸附,降幅为19.20%~37.50%,而对Pb2＋的吸附能力几乎没有影响,降幅仅为0.41%~2.83%。膨润土对4种重金属离子的富集系数,其大小顺序依次为Pb2＋〉Cu2＋〉Zn2＋〉Cd2＋。该选择性吸附顺序与重金属离子的一级水解常数密切相关。

The influence of bentonite on the competitive adsorption characteristic of Cd2＋,Zn2＋,Cu2＋ and Pb2＋ were studied under the conditions of pH=6,T=25℃ and low concentration of heavy metals.The results showed that adsorption of lead ions was decreased insignificantly in competitive adsorption condition,whereas a dramatic decrease was observed on the adsorption of cadmium ions by the presence of lead,copper and zinc ions.As compare to single system the enrichment coefficients of Cd2＋ ions in competitive system reduced by 19.20%-37.50%,while Pb2＋ ions reduced by 0.41%-2.83%.The enrichment coefficients of Cd2＋,Zn2＋,Cu2＋ and Pb2＋ ions by bentonite follow the descending order： Pb2＋Cu2＋Zn2＋Cd2＋.There was a good correction between this order and first hydrolysis constants of heavy metal ions.